1. Field of the Invention
The present invention relates to a method and an apparatus for the measurement of a molecular weight of a polymer including an oligomer.
2. Description of the Related Art
When a molecular weight of a polymer is measured, a viscosity-average molecular weight (M.eta.) is generally used. Measurement of the viscosity-average molecular weight comprises measuring the viscosity of a diluted solution of the polymer using a commercial Ubelohde-type capillary viscometer and then calculating the molecular weight from a viscosity value with a specific equation for the specific polymer which defines a relationship between the viscosity and the polymer molecular weight. This method of measurement is sometimes referred to as the "Ubelohde method".
In order to carry out such a molecular weight measurement in which the viscosity measurement is utilized, it is required to pretreat, for example, dilute and purify, a polymer sample, so that it takes about from one to two hours to obtain measurement results. In addition, strict temperature control during the measurement, such as 30.degree..+-.0.25.degree. C., is necessary. Also, less skill of the measurement gives data with a larger error. In a polymerization operation, such viscosity measurement is carried out after the pretreatment of the polymer which is sampled from a reactor, and then it should be determined whether a desired polymer molecular weight is reached on the basis of the result of the viscosity measurement. If the desired molecular weight has not been reached, the polymerization operation should be continued.
As described above, when the molecular weight measurement is carried out in which the viscosity measurement is utilized, time-consuming manual analyses are required and errors can occur due to the unskillfulness of the individual operator so that the polymerization period can vary depending on the individual operator.